Skin packaging can be classified as a vacuum forming process for thermoformable polymeric films. The product on a supporting member serves as the mold for the thermoformable film which is formed about the product by means of differential air pressure. However, the term "vacuum skin packaging" or VSP as it is referred to hereinafter, refers not to the fact that the thermoformable film is formed around the product by vacuum or differential air pressure but to the fact that the product is packaged under vacuum and the space containing the product is evacuated from gases. Thus, there is a need for the film formed around the product and for the support member to be a barrier to oxygen, air, and other gases.
Various skin packaging processes are disclosed in e.g. French Patent No. 1,258,357, French Patent No. 1,286,018 (LaRoach Freres), Australian Patent No. 245,774 (Colbros Proprietary Limited), U.S. Pat. No. 3,491,504 (W. E. Young et all, U.S. Pat. No. RE.30,009 (Perdue et al), U.S. Pat. No. 3,574,642 (Weinke), U.S. Pat. No. 3,681,092 (Titchness et al), U.S. Pat. No. 3,713,849 (Grindrod et al), and U.S. Pat. No. 4,055,672 (Hirsch et al). The Cryovac Division of W.R. Grace & Co. has sold skin packaging thermoplastic materials under the designations LDX-2986, V834HB, and V836HB. LDX-2986 is of the structure: EVA(28% VA)+antiblock/EVA+ionomer/ethylene alpha olefin/EVOH/tie/EVOH/tie/EVA+ionomer/HDPE. V834HB and V836HB are the same structure except V834HB is 4 mil thick and V836HB is 6 mil thick. The structure is: 5% antiblock+95% ethylene butene copolymer/ionomer/EVA/tie/EVOH/tie/EVA/ionomer/HDPE. Tie is jargon in the industry for an adhesive layer.
In order readily to open packages where plastic film layers have been sealed together to close the package, various tear tabs and easy open mechanisms have been devised. Exemplary are U.S. Pat. No. 4,889,731 (Williams, Jr.), U.S. Pat. No. 4,638,913 (Howe, Jr.), U.S. Pat. No. 4,886,690 (Davis et al), and U.S. Pat. No. 4,956,212 (Bekele). It is a further object of the present invention to provide an improved peelable barrier film for vacuum skin packages having a permeable layer with a high oxygen transmission rate and an impermeable layer with a low oxygen transmission rate such that fresh meat packaged with such film exhibits extended shelf life and improved bloom.
The foregoing and other objects are achieved by the present invention which is described in the Summary of Invention below, shown in the attached Drawings, and further described in the Detailed Description.